1. Field of the Invention
The present invention relates to a film forming method and a film forming apparatus for supplying a processing solution to a substrate to form a film of the processing solution on the front surface of the substrate.
2. Description of the Related Art
In processes of semiconductor device fabrication, a so-called multilayer interconnection process in which multilayered aluminum electrodes are formed on the front face of a semiconductor wafer (referred to as xe2x80x9ca waferxe2x80x9d hereinafter), for example, is performed. An inter-level insulation film, for example, a polyimide film is formed between the aluminum electrodes.
It is required to form the polyimide film uniformly for preventing a drop in yield of products. The formation of the uniform polyimide film is also indispensable for the performance of uniform exposure processing, etching processing, and the like in the lithography process after the multilayer interconnection process. In forming the uniform polyimide film, a spin coating method, for instance, has been adopted so far. The spin coating method is a method in which a polyimide in liquid form is supplied to the front surface of a wafer, the wafer is then rotated, and that the polyimide on the wafer is diffused and applied by centrifugal force due to the rotation.
So-called side rinse processing in which a cleaner such as a solvent for polyimide (hereinafter referred to as xe2x80x9ca solventxe2x80x9d) is supplied to a peripheral edge portion of a wafer on which the polyimide film is formed by the spin coating method to remove the polyimide film at the peripheral edge portion of the wafer is conventionally performed, thereby preventing the polyimide film at the peripheral edge portion of the wafer from adhering to tweezers which support the peripheral edge portion of the wafer and contaminating the tweezers.
A polyimide film, however, has high fluidity, and thus the polyimide film on the side of the central portion of a wafer which has not dried yet sometimes flows out to the side of a peripheral edge portion of the wafer. Therefore, there arises a possibility that even though the aforesaid side rinse processing is performed, the polyimide which there after flows out to the side of the peripheral edge portion of the wafer adheres to the tweezers and contaminates them.
An object of the present invention is to provide a film forming method and a film forming apparatus which prevent a processing solution from flowing out to the peripheral edge portion and thus prevent a supporting member such as tweezers for supporting a substrate from being contaminated, even if a substrate is moved before the processing solution for forming a thin film completely dries after a thin film such as a polyimide film is formed.
To attain the above object, a film forming method of the present invention comprises the steps of supplying a processing solution to a substrate to form a film of the processing solution with a predetermined thickness on the front surface of the substrate, removing the film of the processing solution formed at a peripheral edge portion of the substrate, and solidifying the film of the processing solution formed at a peripheral portion on the inside of the peripheral edge portion of the substrate.
A film forming apparatus of the present invention comprises means for supplying a processing solution to a substrate to form a film of the processing solution with a predetermined thickness on the front surface of the substrate, means for removing the film of the processing solution formed at a peripheral edge portion of the substrate, and means for solidifying the film of the processing solution formed at a peripheral portion on the inside of the peripheral edge portion of the substrate.
In the present invention, for example, after a cleaner is supplied to the peripheral edge portion of the substrate to dissolve and remove the film of the processing solution at the peripheral edge portion; a laser beam is irradiated to the peripheral portion of the substrate to heat and solidify an edge of the peripheral portion of the film of the processing solution. Accordingly, a so-called weir is formed by a solidified portion of the processing solution at the peripheral portion of the substrate. Consequently, the outflow of the processing solution on the side of the central portion of the substrate which has not dried yet is prevented by the solidified portion. Here, xe2x80x9ca peripheral edge portionxe2x80x9d means, for example, a side peripheral end face and an edge portion of the wafer, and a portion at which a semiconductor device or the like is not formed in the following processes, and xe2x80x9ca peripheral portionxe2x80x9d means, for example, a portion located on the inside of the above xe2x80x9cperipheral edge portionxe2x80x9d of the wafer.